What are the usual concentrations of plant hormones that are effective, and what kind of effects do they have on different plant tissues?

A) They are effective only in extremely large concentrations, and they have the same effect on different plant tissues.
B) They are effective at low concentrations, and they have different effects on different plant tissues.
C) They are effective at low concentrations, and they have the same effect on different plant tissues.
D) They are effective only in extremely large concentrations, and they have different effects on different plant tissues.